This proposal requests continued support for a program of research on perlingually deaf children with cochlear implants. The long-term goal of the project is to assess the effect of cochlear implants (CIs) on the development of speech production and language. In particular, we will compare the speech and language abilities of CI users to those of hearing aid (HA) users to determine the potential benefits of implantation compared to HA use. We will also compare the performance of children implanted early (below age 3-4) to those implanted later in life, to investigate whether early implantation may limit the negative consequences of auditory deprivation in the development of language and speech production. We will also study the influence of communication mode on speech and language development by comparing the performance of users of oral communication with users of total communication. We also plan to assess whether the latest clinically available processing strategies will allow children to reach superior levels of speech and language development, compared to older stimulation strategies. Finally, the proposed studies will provide information that will improve our basic understanding about the relation between the development of speech perception and speech production and about the development of language in children receiving impoverished auditory input. These goals will be achieved by a longitudinal assessment and description of the speech production and language abilities of a large group of deaf children, and by more intensive studies that focus on a smaller number of subjects. The proposed research extends our earlier work on speech production in a number of new directions. Project I will study the acoustic and physiological characteristics of the speech of implanted children and normal-hearing control subjects. Project II will examine the acquisition of English phonology by implanted children. Project III will assess the longitudinal changes in speech intelligibility by children with CIs and control groups of profoundly deaf children with hearing aids. Finally, Project IV will investigate the language development of implanted children and compare their performance to unimplanted deaf controls and normal-hearing children. The four projects of the proposed research address the efficacy of CIs in facilitating the development of specific abilities that all children must acquire to develop spoken language: the ability to control the physiological mechanisms used in speech production, to organize speech sounds into a coherent phonological system, to produce intelligible speech, and to control the creative, meaningful aspects of language.